The present invention concerns a sickleless internal gear pump having a ring gear and pinion for generating high pressure. A pump of this categorial design is known particularly as an embodiment from DE 41 04 397 A1.
Internal gear pumps generally feature an internal ring gear with which an external pinion with a smaller number of teeth is in mesh, i.e., engages the ring gear in driving fashion. Normally, the teeth of such pumps--based on the diameter of the pinion or ring gear--is relatively narrow so that--once the volume flow to be pumped has been determined by the height of the teeth and the width of the gears--this volume flow is for design reasons limited with popular pumps. Sickleless internal gear pumps specifically have the advantage of a minimal size.
For improving the tightness between the tooth heads of pinion and ring gear, DE 41 04 397 A1 already has proposed to insert a sealing element in each of the tooth heads of one of the two gears. These sealing elements are on the backside in contact with the pressure range so that, as the gears mesh, they bear in sealing fashion on the tooth head of always the other gear.
However, on the sickleless internal gear pump known from DE 41 04 397 A1, only a line seal is created in the area of pressure buildup on the tooth heads, according to the geometric shape of the sealing elements. With unfavorable conditions due to tolerance variations, spacing changes or variations of the internal diameter, as the case may be, a result of this is that the tightness of internal gear pumps is lacking. This is equivalent to a loss of pumped medium, a drop of the volumetric efficiency, an increase of pressure pulsation and, finally, an increase of the noise level of the pump in operation. The more favorable gap conditions required for a remedy in the area of the tooth head seal in the pressure buildup could be realized only at an extremely high manufacturing expense.
The problem underlying the present invention is to propose a sickleless internal gear pump of the categorial type where the sealing effect in the pressure buildup between opposed tooth heads of the gears is improved without causing the manufacturing expense to rise over proportionally, and with the result that the aforementioned shortcomings (pressure pulsation, noise) will be eliminated.
This problem is solved in that the sealing element is in the area of the sliding surface so dimensioned that it occupies the entire head surface of the tooth head of the ring gear or pinion.
The present invention is in the final analysis constituted by replacing the tooth heads of the ring gear or pinion quasi by an equivalent, i.e., equally acting insert which on grounds of its specific fashioning, or shaping, realizes in the pressure buildup area a surface seal, thereby ensuring a minimal gap between pinion head and ring gear head. This improves also the volumetric efficiency, with the final result that the internal gear pump is suited for elevated pressures. Likewise, the extreme efforts toward gap minimization as required in the manufacture or assembly of an internal gear pump are eliminated; eliminating for instance the joint finishing of the plain bearings of the bearing covers of an internal gear pump. In view of the production of ring gears it should be noted that the expensive and complex form grinding of the internal tooth head shape can be dispensed with, because that shape is realized by an insert which is manufactured separately, and thus more cost-effectively.
A particular advantage of the inventional concept is constituted in that, by way of the radial compensation achieved, a more suitable pressure buildup control is possible via control slots.